public bool Unload(IService service)
        {
            if (!this.CanUnload(service))
            {
                Debug.WriteLine(this + ": kann " + service + "nicht entladen");
                return false;
            }

            Debug.WriteLine(this + ": entlade " + service.GetType()  + "...");
            if (service.Loaded)
                service.Unload();

            this.services.Remove(service.GetType());
            return true;
        }